The circulating fluidized bed boiler is a boiler which combusts coals and other low grade fuels using a principle of circulating fluidized bed reactor. As illustrated in FIG. 1, the circulating fluidized bed boiler is mainly composed of a furnace, a cyclone separator, a loop seal, a flue gas channel, a deduster, an induced draft fan, etc. The circulating fluidized bed boiler is widely used in the fields of industrial steam supply and thermal power generation, and it has prominent advantages in the aspects of environmental protection and pollutant comprehensive treatment.
The material balance system is apparatus and component for maintaining the gas-solid flow condition in the circulating fluidized bed boiler, and the cyclone separator is the critical component of the material balance system in the circulating fluidized bed boiler. The separation efficiency is an important index reflecting the separation performance of the cyclone separator, and the higher the separation efficiency, the better the separation performance. Therefore, the separation performance of the cyclone separator can be determined through a calculation of the separation efficiency. The separation efficiency may be acquired by directly calculating material concentrations (mass of solid particles contained in the gas of unit volume) at an inlet and an outlet of the cyclone separator. For example, a patent solution with an application number CN200910024109.8 proposes the following measurement method: obtaining a material concentration ρin at the inlet of the cyclone separator by measuring a pressure difference between a middle portion and an upper portion of the boiler furnace, and obtaining a material concentration ρout at the outlet of the cyclone separator by measuring a flue flow rate at the outlet of the cyclone separator, then calculating the separation efficiency of the cyclone separator as cyc=(1−ρout/ρin)×100%, and finally analyzing the separation performance of the cyclone separator according to the separation efficiency. The method analyzes the separation performance by directly calculating the separation efficiency. But in commercial units, it is difficult to accurately calculate the material concentration at the inlet of the cyclone separator according to the pressure difference between the middle portion and the upper portion of the boiler furnace, and it is also hard to measure the flue flow rate and the material concentration at the outlet of the cyclone separator under the condition of the prior art, and the measurement process will interfere with the gas flow and combustion in the boiler, thus the method is not so practically operable.
It is important to determine the separation efficiency of the cyclone separator, so as to guide the boiler operation, and ensure stable flow and combustion state in the circulating fluidized bed boiler. However, at present, measures for effectively measuring the separation efficiency of the cyclone separator are absent.